Acromegaly: GH Response Pattern to Oral Glucose Load and Personalized Medicine

Michio OtsukiJapan Speaker Acromegaly: GH Response Pattern to Oral Glucose Load and Personalized MedicineAcromegaly is characterized by elevated levels of growth hormone (GH) and insulin-like growth factor-1 (IGF-1), with resultant signs and symptoms of hypersomatotropism. To examine autonomous secretion of GH, an oral glucose tolerance test (OGTT) is used. In most healthy individuals, GH levels decrease to a nadir below 0.4 mg/L after OGTT. In contrast, patients with acromegaly fail to suppress serum GH levels after OGTT. Interestingly, a paradoxical GH response to oral glucose (OG) load is found in one third of acromegalic patients. The mechanism of this paradoxical response in acromegaly is mediated by glucose-dependent insulinotropic polypeptide, which is released after OG administration We found that the paradoxical GH response to OG load reflected the clinical characteristics. The patients the paradoxical GH response to OG load (OG responders) had substantially greater IGF-1 SD scores than nonresponders. Regarding glucose metabolism, 120-minute plasma glucose and immunoreactive insulin after OG administration and hemoglobin A1c were significantly greater in OG responders than in nonresponders. GH levels during octreotide or bromocriptine testing were decreased more significantly in OG responders than in nonresponder. The proportion of pituitary tumors with hypointensity on T2-weighted MRI was significantly greater in OG responders than in nonresponders. OGTT is essential to evaluate autonomous secretion of GH. The paradoxical GH response to OG load is the useful for evaluation of the clinical characteristics of acromegaly and leads to the personalized medicine of acromegaly.